Rotary-type disc drives are well-known which include an actuator block rotationally coupled to a chassis of a disc drive for supporting a plurality of heads relative to selected data tracks of the disc surface. The rotary actuator is operated via a voice coil motor operably coupled to the actuator block. Typically, the voice coil motor includes a voice coil coupled to the actuator block and a magnet-and-backiron structure coupled to the chassis of the disc drive for providing a permanent magnetic field for operation of the voice coil motor. Current is supplied to the coil of the voice coil to move the voice coil motor within the magnetic field formed by the magnet-and-backiron structure.
The actuator block is rotationally coupled to the chassis via a bearing cartridge in a known manner. Operation of the voice coil motor is controlled via control circuitry of the disc drive. Current is supplied to the voice coil motor to rotate the actuator block for placement of the heads relative to selected data tracks. Disc drive areal density is increasing such that precision head placement is required via operation of the voice coil motor. Additionally, there is an effort to provide faster seek times for positioning the heads to retrieve data. Structural dynamics of an actuator limit servo-bandwidth, thus limiting rejection of external disturbances, as well as degrading head placement during seek settle and track following modes. Thus, it is desirable to provide an actuator assembly capable of supporting high servo bandwidth for improved seek times and track following capability. The present invention addresses these and other problems, and offers other advantages over the prior art.